This invention relates to a type of optical apparatus for use in a containment vessel or chamber. The apparatus is capable of maintaining its external optical surface free from dust and other contaminants which could effect the clarity of the optical image coming from inside the containment chamber. When an optical probe is used in conjunction with a containment vessel hazardous materials often make maintaining a clean optical surface difficult, and the lack of a clean surface results in a reduction, to varying degrees, of the amount of light passing through the lens or other optical instrument. This device employs a distinct fluid flow pattern to maintain optical clarity and can be used in a gas or liquid environment, and the contaminants can be in the form of either a gas, liquid or solid.
The subject apparatus employs the use of an inert transpiration fluid to keep the optics free from surface contamination. This fluid is dispersed in a symmetrical manner in front of the exposed optical surface to form an optical purge. The purge functions to keep the optical surface clean and thus, free from contaminants which allows for clear viewing. This is accomplished by providing a transpiration fluid from a source outside the containment vessel and flowing the fluid through an annulus formed by the use of two concentric tubes leading to a porous opening located directly in front of the optical lens which is located in the contamination chamber. The temperature, pressure, and flow rate of the transpiration fluid are controlled using apparatus located outside the containment vessel. These fluid properties can be varied to provide for optimum conditions relative to the type of contaminants and the conditions present in the containment vessel. This ability to control the temperature, pressure and flow rate of the transpiration fluid allow the operator to provide a transpiration fluid having steady physical properties, or in the case where the conditions in the containment vessel are changing, a transpiration fluid having variable properties to allow the fluid properties to match the conditions in the containment vessel in a time varying manner.
Once the fluid exits the tubular annulus through the porous cylindrical sleeve, it is positioned directly in front of the optical surface. This arrangement causes the fluid to flow radially inward and then axially away from the optical surface. This pattern of flow by the transpiration fluid prevents any dust or other contaminants which are floating in the vessel from depositing on the optical surface and restricting its imaging capability; this is accomplished by producing a fluid flow which is directed axially away from the center of the optical surface. With this apparatus, the transpiration fluid can be either a liquid or a gas.
Other devices which use discrete orifices in an attempt to keep the optical surface clean tend to entrain contaminants and carry them to the vicinity of the optical surface.
Thus, it is an object of this invention to provide an apparatus for keeping the optical surface associated with an optical probe free of contaminants,
A further object of this invention is to provide an apparatus in which the transpiration fluid can be either a liquid or a gas depending on the substance contained in the containment vessel.
Additional advantages, objects and novel features of the invention will become apparent to those skilled in the art upon examination of the following and by practice of the invention.
This invention comprises an apparatus for keeping the exposed optical surface of an optical probe free of contaminants when it is positioned in a containment vessel. The apparatus directs a transpiration fluid down a cylindrical annulus to a porous inner cylindrical sleeve which then directs the transpiration fluid radially inward towards the central axis of the optical surface, thus, keeping the surface free from the depositions of contaminants on its surface. With this apparatus, either a liquid or a gas can be used as the transpiration fluid and the temperature and pressure of the fluid controlled to provide for either steady conditions or time varying conditions.